You cannot launch your API directly as it is protected with mutual TLS certificates. You can only access/test the API via a client application with the proper credentials. This behavior is by design to protect/secure your APIs for unauthorized access. So here are the high level steps that happens when you publish your API to Bluemix:
1) Youcreate your API using the API Designer (i.e. by calling "apic edit" on your command line).
2) While working on the API Designer you can test your api locally by running it on the Micro Gateway. It runs the application locally and you run curl requests to test it (or even other tools like Postman)
3) You then publish your API to Bluemix
4) It is published with a mutual TLS certificate (for domain *.apic.mybluemix.net)
5) Client certificate is uploaded to the API Gateway (Data Power Gateway), so only when you call the API via the published end point it will work.
At this point to further test your API you have to subscribe to a plan in your developer portal, or if you are using a Sandbox catalog you can use the default Client ID and Client Secret provided in the Settings->Overview session of your API Manager.
